Fabric venetian blind and method of fabrication

ABSTRACT

A method of making a fabric Venetian blind comprises helical winding of a narrow, elongated strip, which, when properly overlapped and bonded along longitudinal glue lines, will form the vanes and front and rear facings of the blind. The strips may be formed of a single, uniform material, or of adjacent, longitudinally extending portions of relatively opaque and relatively translucent fabric. An alternative embodiment uses the same winding technique to similarly form a structure of only translucent fabric, but with pockets for subsequent insertion of opaque vanes. Several alternative strip configurations and assembly arrangements are disclosed. The disclosed method and structure may also be used to form products for other applications.

This is a divisional application of application Ser. No. 09/349,907filed on Jul. 8, 1999, Pat. No. 6,302,982, which is a continuation inpart of abandoned application Ser. No. 09/288,389 filed on Apr. 8, 1999which is a continuation in part of application Ser. No. 08/947,608 filedOct. 9, 1997, Pat. No. 6,024,819.

FIELD OF INVENTION

This invention relates to window coverings, and more particularly to thefield of Venetian blinds having front and rear panels of sheer ortranslucent fabric between which are arrayed a series of relativelyopaque fabric slats or vanes which can be tilted for light control bymeans of limited rotation of a wind-up roll to which the front and rearpanels are connected. The invention includes an improved product,fabricating technique and apparatus for fabricating such blinds, whichtechnique can also be applied to forming multi-layered composite sheetsused in other types of products and for other purposes.

BACKGROUND OF THE INVENTION

The most familiar type of Venetian blind window covering comprises aseries of rigid slats or vanes suspended and controlled by a ladder cordsystem. The slats are typically wood, plastic or metal, and rest on theladder cord rungs. The rungs are secured to front and rear verticalcords whose upper ends are secured to circumferentially spaced locationson a wheel. Limited rotation of the wheel, by means of a control wand orcords, causes relative motion between the front and rear cords, which inturn tilts the rungs and vanes. The entire array can be raised andlowered by additional cords which act to lift a bottom rail.

A modified type of Venetian blind is disclosed in U.S. Pat. No.3,384,519 to Froget. There, the ladder cord system is replaced by frontand rear cloth panels to which the vanes are heat welded. Preferably,the cloth panels and vanes are all made of thermoplastic yarns, tofacilitate bonding by heat welding. Partial rotation of an upper drum,to which the panels are connected, shifts the panels relative to eachother, thereby causing the vanes to tilt for light control. Anothersimilar product is disclosed in French Patent No. 1,521,488 to Demerson.Demerson prefers films to woven fabrics, and discloses adhesive bondingof the vanes to the facing panels.

Several more recent patents are directed to modifications of Froget'sbasic idea, wherein the vanes are made of flexible fabric, adhesivelybonded to the front and back panels. Additionally, the entire array canbe retracted from the window opening by winding it onto an upper wind-uproller by means of cords which lift a bottom rail. Representative ofthese patents are U.S. Pat, Nos. 5,287,908, 5,313,999, 5,320,154,5,394,922 and 5,456,304, all assigned to Hunter Douglas, Inc., and apatent to Ren Judkins patent, No. 5,339,882.

U.S. Pat. No. 5,664,613 (and subsequently assigned to a company owned bythe assignee of the present application) describes another form ofconstruction for a fabric Venetian blind. A continuous panel ofrelatively translucent material forms one facing of the blind. To thatpanel is bonded a series of parallel fabric strips at uniform intervals.Each strip comprises two adjacent portions of dissimilar material, onebeing relatively translucent and the other relatively opaque. The freeedge of the opaque portion is bonded to the facing panel, while the freeedge of the translucent portion is bonded to the adjacent strip at thejunction line of that strip's two portions. The assembled translucentportions of the constituent strips become the second facing panel of thecompleted blind. That is, the second facing panel, rather than being asingle continuous panel of fabric, is a composite of several parallelstrips, each having a height dimension approximately equal to the width(or depth) of the vanes.

U.S. Pat. No. 5,888,639, assigned to Newell Operating Co., discloses inFIGS. 15-19 a fabric Venetian blind having a structure very similar tothat disclosed in FIGS. 3-6 of my parent application, Ser. No.08/947,608, filed Oct. 9, 1997 (which Figures are also found in thepresent application). As in my parent application, the product is alaminated assembly of previously formed three-element strips. However,the relationship of the individual components of each three-elementstrip, a and the method of preparing each such strip for subsequentassembly to adjacent strips, is substantially different. Furthermore,the method of assembly of the three-element strips to each other issubstantially different, in that the strips are cut to a predeterminedlength, prior to their lamination to each other, which lengthcorresponds to the desired width of the fabric Venetian blind. Themethod of assembly disclosed in my parent application and herein,wherein the three-element strip is helically wound upon itself inpartially overlapping successive layers, represents a substantialimprovement in the speed and economy of manufacture.

U.S. Pat. Nos. 5,490,553 and 5,603,369, assigned to Hunter Douglas,disclose in FIGS. 16-19 a vertical blind wherein each vertical blindvane is formed of the same strip of material as an adjoining portion ofa facing panel on one side of the vanes. The single facing is acomposite of narrow vertical strips. The vane portion of this strip isdoubled back on itself. Another patent assigned to Hunter Douglas, No.5,638,880, discloses in FIG. 26 a vertical blind wherein the facing onone side of the vanes comprises a series of vertical strips of material,each joined along one vertical edge to an adjacent strip, and at theother vertical edge to both the adjacent facing strip on that side and adiscrete piece of substantially rigid, planar material forming the vane.The patent further discloses that both a front and a rear facing may befabricated of such strips, and the strips and vanes can be oriented ineither the vertical or horizontal directions.

U.S. Pat. No. 4,631,217, also assigned to Hunter Douglas, discloses inFIG. 2 a honeycomb or cellular type of window covering wherein a seriesof pleated, generally Z-shaped strips, each formed of a single piece offabric, are bonded together in a manner whereby each strip forms thefront portion of one cell, the rear portion of an adjacent cell, and adividing wall between the two cells. The dividing walls, however, areincapable of functioning as the vanes of a Venetian blind type ofproduct, because they remain substantially perpendicular to the frontand rear faces of the window covering throughout the full range ofexpansion and collapse of the cells.

Known processes for manufacturing these prior art fabric Venetian blindsare complex, slow and costly, and have contributed to a high price forthese otherwise attractive products.

Accordingly, it is a principal object of the present invention to createadditional alternative three-element or multi-element stripconfigurations and bonding procedures which also lend themselves to theuse of the more economical helical winding technique disclosed in myabove-mentioned parent application.

SUMMARY OF THE INVENTION

The presently contemplated application for the disclosed invention isthe formation of fabric Venetian blinds, using a technique of helicallywinding an elongated strip of fabric. In one embodiment of the Venetianblind, a three-portion strip is initially formed from threeside-by-side, longitudinal, bands or portions of approximately equalwidth and length. Each edge of the central portion is joined byultrasonic welding to an edge of the adjacent outer portion. The outerportions are formed of sheer or relatively transparent material, and thecentral portion is relatively opaque.

As a result of the helical winding process, the central portion becomesthe blind vane, while the two outer portions ultimately become segmentsof the front and rear composite facings of the blind. Successivewindings are staggered and partially overlapped so that two of the threeportions of the underlying winding are covered by the overlying winding.Two longitudinally extending glue lines are applied along the undersideof the infeeding overlapping strip, these being positioned to bondtogether adjacent windings. A tube-like wound structure is formed which,when cut open along a line perpendicular to the helix angle, will resultin a fabric Venetian blind. The disclosed method of fabrication thusdiffers significantly from the prior art. Indeed, this product and itsbenefits could not so economically be achieved by known manufacturingprocesses.

The strips, once assembled by the winding operation, produce both theflexible vanes and the front and rear face panels in a single continuousprocess. The resulting composite face panels comprise narrow, horizontalstrips which have been joined successively to one another in the windingoperation. The resulting flexible vanes swing between light-admittingand light-blocking positions upon relative movement between the twocomposite face panels.

Alternative constructions may include an additional layer of fabric inthe vane portion, to create a pocket into which an opaque insert cansubsequently be inserted, and the formation of products having multiplerows of vanes or central ligaments.

Another alternative construction relates to a modified three-elementstrip configuration wherein the entirety of one sheer strip more fullyoverlaps the relatively opaque vane strip, with one edge substantiallyaligned with a first edge of the vane and ultrasonically welded thereto,while the other sheer strip is slightly lapped under and ultrasonicallywelded to the second edge of the vane. The vane is slightly wider thaneach of the sheer strips, permitting the vane to be simultaneouslywelded to each of the sheers without interference by overlapping theother sheer at the desired weld zone.

The novel winding technique disclosed herein may also be used tofabricate products from other types of materials or intended for otherfields of use. For example, multi-layered materials made from thermallynon-conductive or reflective material may be made for insulationapplications; polarized or tinted films may be used to create desiredoptical effects; and materials of selected porosity may be used to formair filtration products.

Also disclosed is the use of a resiliently deformable circumferentialsurface on a nip roll which functions to steer the sheet-like materialwhich is driven by the roll set when differential pressure is applied tothe two ends of the deformable roll.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified perspective view of the fabric Venetian blind ofthe present invention, shown with the vanes positioned in their maximumlight-admitting setting.

FIG. 1B is a view similar to FIG. 1A, showing the vanes positioned in apartially closed setting.

FIG. 2 is a side view, in simplified form, of a representative prior artfabric Venetian blind, wherein the vanes are joined to single,continuous-sheet type front and rear sheer panels. The blind is shown inthe fully-open position of the vanes, while a partially closed positionis shown in phantom lines.

FIG. 3 is an enlarged fragmentary side view of the blind of FIG. 1A.

FIG. 4 is an exploded schematic view of the blind of FIG. 3, showing therelationship of adjacent three-portion strips.

FIG. 5 is an enlarged, simplified view of the blind of FIG. 3, with thevertical scale exaggerated to reveal the relationship of adjacentthree-portion strips.

FIG. 6 is a perspective view of a fragment of a three-portion strip suchas used in the embodiments of FIGS. 4 and 5.

FIG. 7 is an exploded end view of a second form of the three-portionstrip.

FIG. 8 is a view similar to FIG. 7, showing a third form ofthree-portion strip.

FIG. 9 is a simplified perspective view of equipment suitable forforming a blind according to FIGS. 3-5 using the process of the presentinvention.

FIG. 10 is a schematic side elevational diagram of the equipment shownin FIG. 9.

FIG. 11 is a simplified plan view of the equipment of FIG. 9, showingthe supporting framework.

FIG. 12 is a simplified side elevational view of the equipment of FIG.11.

FIG. 13 is a perspective view of a helically wound tube of blindmaterial, prior to being cut open, viewed from the opposite end of thespars from the end shown in FIG. 9.

FIG. 14 is a schematic end view, in the direction of the cutting planeC—C, of the helically wound tube showing how it is cut open to form afall-width fabric Venetian blind.

FIG. 15 is a schematic elevational view of nip roll set 66.

FIG. 16 is an end view of the nip roll set of FIG. 15.

FIG. 17 is a plan view of the nip roll set of FIG. 15.

FIG. 18 is a view similar to FIG. 5, showing an alternative embodimenthaving pockets to receive opaque vane inserts.

FIG. 19 is a view similar to FIG. 5, showing still another alternativeembodiment wherein multiple rows of vanes or central ligaments areprovided.

FIG. 20 is a view similar to FIG. 9, showing a modified system forfeeding the fabric strip to the winding equipment.

FIG. 21 is a view similar to FIG. 9, showing another modified system forfeeding the fabric strip to the winding equipment.

FIG. 22 is an enlarged, simplified view, similar to FIG. 3, but showingthe configuration which results from a modified location of the glueline which joins successive three-element strips.

FIG. 23 is an end view, with the vertical scale exaggerated, of a priorart three-element strip configuration.

FIG. 24 is an end view, similar to FIG. 23, showing one of the modifiedthree-element strip configurations of the present invention.

FIG. 25 is a fragmentary perspective view, with the vertical scaleexaggerated, of a portion of the helical winding sequence used inconjunction with the three-element strip configuration of FIG. 24.

FIG. 26 is an enlarged fragmentary side view of the blind which resultsfrom use of the three-element strips of FIG. 24.

FIG. 27 is a view similar to FIG. 26, but showing the configurationwhich results from a modified location of the glue lines which joinsuccessive three-element strips.

FIG. 28 is a view similar to FIG. 25, but showing the glue linesinitially applied to the opposite element of the opposed elements to bejoined.

FIG. 29 is a view similar to FIG. 25, but showing a modified orientationof the three-element strip of FIG. 24 as the strip is fed into thehelical winding apparatus.

FIG. 30 is a fragmentary perspective view of a portion of the windingapparatus adapted for use with the three-element strip of FIGS. 24-26.

FIG. 31 is a fragmentary plan view of a portion of the winding apparatusillustrated in FIG. 30.

FIGS. 32a-32 b through FIGS. 38a-38 b are end views, similar to FIG. 23,showing additional alternative embodiments of three-element stripsaccording to the present invention, and wherein the “a” and “b” figuresof each pair show the strip in its flattened configuration after weldingand in its partially opened, light-admitting configuration (as achievedafter assembly with other such strips in a light-controlling product,respectively.

FIGS. 39a-39 b through FIGS. 42a-42 b are end views, similar to FIGS.32-38, showing still further alternative embodiments, whereintwo-element fabric strips are welded to form a pocket for subsequentreception of an opaque material.

FIG. 43 is an end view, with the vertical scale exaggerated, of amodified three-element strip configuration of the present invention.

FIG. 44 is an enlarged fragmentary side view of the blind which resultsfrom use of the three-element strips of FIG. 43.

DETAILED DESCRIPTION

FIG. 2 of the drawings shows a fabric Venetian blind 20 which, in itsgeneral construction, is typical of the prior art., The solid linesindicate the fully-open position of the vanes. The blind comprises afront facing 22, rear facing 24 and vanes or slats 26. The front andrear facings are each typically formed of a continuous panel of sheermaterial, chosen for its combination of soft, aesthetic appeal, itsability to permit a substantial amount of light to be transmitted whenthe vanes are in their open position, and, depending upon the selectedweave, its ability to permit viewing of scenes through the material. Thevanes are bonded along their respective longitudinal edges to the frontand rear facings. Bonding can be by adhesive or thermal welding. Whenthe wind-up roller from which the blind is suspended is rotatedslightly, the front and rear facings shift in a vertical directionrelative to each other, causing the angle of the vanes to change. Aposition near the fully-closed setting of the vanes is shown in phantomin FIG. 2, with the elements labeled with primed numerals.

FIGS. 1A and 1B show, in simplified form, the basic elements of acomplete fabric Venetian blind assembly 28 in full-open and near-closedconditions, respectively. The blind comprises front and rear sheer orrelatively translucent facings 30,32, respectively, a plurality ofrelatively opaque vanes 34, a wind-up roller 36 and a bottom rail 38.Not shown are the cords or other means for rotating roller 36 to adjustthe vane angle and to roll the shade around the roller to fully exposeall or a portion of the window opening.

Comparing FIGS. 1A and 1B it can be seen how the points of attachment ofthe front and rear facings to opposite sides of the circumference of theroller result in relative vertical movement of the facings, andtherefore adjustment of the vane angle, when the roller is rotatedslightly.

FIG. 3 and the following figures illustrate various novel aspects of thepresent invention. A first embodiment is best shown in FIGS. 4-6.Fabrication begins with the creation of an elongated strip 40 (see FIG.6) comprising at least two dissimilar fabric materials. The outerportions 30′,32′ are formed of relatively translucent or sheer material,while central portion 34 is formed of a relatively opaque material.Outer portions 30′,32′ may be formed of the same or different fabrics.The central portion can be opacified by use of a more densely wovenfabric, or by coating or laminating (see discussion of FIGS. 7 and 8below) or by the use of opaque inserts (see discussion of FIG. 18below). The adjoining edges of these portions may be connected bygluing, ultrasonic welding, thermal bonding or stitching. Ultrasonicwelding is the preferred method, because it is speedy and permitsprecision location of adjoining edges.

To accomplish such welds, the strip portions are made to overlap oneanother in the region to be welded, which overlap is then meltedtogether by a commercially available ultrasonic seam welding device suchas a Seam Master LM 720 or LM 920 manufactured by Sonobond Corporation.By way of example, the overlap may be about 0.10-0.20 inches, with thewelding performed by a stitch-wheel having about one and one-half timesthe pitch of the main knit, in order to assure fiber capture. Acontinuous (rather than stitch knit) will also work if the vane isnon-woven or film material. This process also beneficially compressesthe welded zone and destroys the fabric interstices, so that the jointwill not be porous to subsequently applied glue lines. Thus, unsightlybleed-through of the glue lines is avoided. The width of strip 40 isapproximately three times the desired vane width (i.e., blind thicknessin the fully open setting of the vanes). It should be noted that theillustrations of FIGS. 4-6, for simplicity, show the three-elementstrips as if they are each an entirely coplanar composite structure,without_overlapping junctions at the adjoining edges of their individualcomponent strips,. In practice, it is preferred that the vane overlapsone sheer and underlaps the other sheer, with the strips beingoverlapped with adjacent three-element strips so that the sheer of onestrip overlaps and is directly glued to the sheer of the preceding andsucceeding strips.

Unlike known processes of the prior art, the fabric Venetian blind ofthe present invention is generated by helically winding the strip uponitself, in partially overlapping fashion, with each winding being bondedto the preceding winding along uniformly located longitudinal bondinglines. The result is that each winding of strip material 40 constitutesone vane and an adjacent fragment of each of the front and rear facingsof the completed fabric Venetian blind.

The relationship of adjacent windings of strips 40 of this firstembodiment is best seen in FIGS. 4 and 5. Each strip winding 40 overlapsapproximately two-thirds of the preceding strip winding. Specifically,the leading edge (i.e., the right edge as viewed in FIG. 6) of a windingis placed at or near the sheer/opaque junction of the preceding winding.A previously applied front glue line 42 is located on the underside ofthe upper strip at that contact line, while a previously applied rearglue line 44 is located at the underside of the upper strip at or nearthe junction between the rear sheer portion 32′ and the opacified vaneportion 34. That rear glue line 44 will then join such strip to thetrailing edge of the previously wound or lower strip 40.

The choice of location of glue lines 42 and 44 relative to the junctionsbetween the sheer and relatively opaque portions of each winding is notcritical. FIG. 22 shows the identical three-element strip illustrated inFIG. 5, but with the front and rear glue lines 42″, 44″, respectively,shifted laterally away from the junction between the respective sheerand relatively opaque portions of each three-element strip. Thatrelocation of the glue lines creates short tab-like extensions 43″, 45″of the respective sheer portions, which tabs project into the interiorof the cells defined as by the sheers and vanes.

Initial indications are that these tab-like extensions 43″, 45″ appearto be beneficial. Fabric Venetian blinds which have the vane materialconnected essentially directly to the planes of the front and rearfacings have a tendency not to fully close in the overlapping,light-blocking position. This phenomenon appears to result from the“memory” which the vanes retain of their shape in the open position.However, the optional use of sheer tabs 43″, 45″, resulting fromrelocation of the glue lines, places much less resilient sheer materialin these flexing or hinging zones. The reduced memory and/or resilienceof the sheer material allows the relatively opaque vanes to lay flatlyagainst the faces, even if there is some residual splay in the weldjoints. This benefit is even greater where the tab extends in thereverse direction from the vane, as in the case of the upper tabs shownin FIG. 27 as compared with the lower tabs of that Figure.

Furthermore, if the extreme edge of the center opaque vane (outboard ofits weld to the sheer tab) overlays the sheer tab to a substantialdegree, as is typical, then the reverse-style tab beneficially acts as abuttress against the facing when the vanes are pulled into the open,view-through position. The Vane must then adopt greater transverse flexand curvature, which is an established aesthetic benefit, rather thanlocally hinging as a stiff and flat element from the facing at the muchsofter sheer tab.

As exemplified by the configuration of FIG. 22, the relatively opaqueportions need not fully span the distance between the front and rearfacings, as long as the opaque portions overlap when the blind is in thefully closed position. Glue lines 42 and 44 may be spaced from theexposed, exterior edges of the strips, if desired, as when a series ofunsupported, fringe-like bands are desired on one or both of the facingpanels.

Alternative forms of the three-portion strip 40 are shown in FIGS. 7 and8. In FIG. 7, the strip is formed of a full-width relatively translucentportion 46, with a relatively opaque central portion 48 laminated to itby any of the previously described joining techniques. This embodimentis not preferred, because it tends to be too stiff to hang uniformly. Inthe FIG. 8 embodiment, the three-portion strip is formed of a singlepiece of fabric, but with less dense weaving patterns being used for theouter portions 50, and a more dense or opaque weaving pattern being usedfor the central portion 52 which will become the vane of the finishedblind. The embodiments of FIGS. 6 and 8 are preferred, because they tendto hang in a more uniform, wrinkle-free manner.

The method and equipment employed for fabricating the embodiment ofFIGS. 3-5 is illustrated in FIGS. 9-17 of the drawings. Themanufacturing equipment includes a pair of parallel, non-rotating spars56,58 skewed at an angle to two parallel nip roll sets. The first niproll set 60 serves to drive the fabric by tensioning the upper reach offabric tube 88. Nip roll set 60 comprises a lower, motor-driven roll 62and an upper, pressure roll 64. The second nip roll set 66 serves toprovide tensioning drag and to steer fabric tube 88. It comprises alower, motor-driven roll 68 (which is driven in a manner to tension orbrake the span of fabric between it and drive nip roll set 60) and anupper, steering pressure roll 70. The steering action is describedbelow. Rolls 62 and 68 may be driven by belt-driven sprockets (notshown). The fabric between nip sets is thus held flat and substantiallyplanar for attachment of the infeeding strip, assuring that the finalproduct will also lie flat.

The three-portion fabric strip 40 is fed from strip supply roll 72,which has its own drive motor M which drives roll 72 at a speedcontrolled by the position of dancer 73. If the strip loop around dancer73 gets smaller, the motor driving roll 72 speeds up to maintain auniform amount of strip in that portion of the strip feed system. Strip40 continues from dancer 73 through a nip roll set comprising upper roll74 and lower motor-driven roll 75 to tension-sensing roll 76, which isprovided with a load cell on its axle. This load cell senses tension inthe strip between rolls 76 and 64, and adjusts the speed of motor Massociated with nip roll 75 to maintain the desired tension in thatportion of the in-feeding strip.

Two adjacent glue applicators 78 apply continuous beads of glue 42,44 tostrip 40.

The support structure for the two pairs of nip rolls 60,66 comprisesmain mounting plate 80 (see FIGS. 11-12) and end plate 82 connectedthereto by cantilevered beams. End plate 82 supports the end of upperrolls 64,70 remote from main plate 80, while lower rolls 62, 68 aresupported by similar cantilevered beams and end plate 82′. These endplates must be supported in this fashion so that no support structurecrosses from inside to outside the fabric loop or tube 88 defined byspars 56, 58. Spars 56,58 are cantilevered from a separate framestructure 84, which can be pivoted about vertical axle 86 to permit thespars to be set at a predetermined angle relative to the two nip rollsets. This angle is a function of the desired lead angle for the helicalwinding of strip 40, as will be explained below. Appropriate clearanceholes are placed in frame 84 to permit passage of spars 56,58. The endof cantilevered spars remote from mounting frame 84 is free ofconnection to supporting structure to permit removal of the continuouslyformed fabric tube therefrom and to allow adjustment of the spar anglerelative to the lower rolls. Alternatively, if spar angle adjustmentwere deemed unnecessary, the ends of the spars could be attached to thelower roll support or to any other structure lying entirely withinfabric loop 88. Alternatively, the spars can extend far beyond thelongest desired window shade and be supported to ground at both ends. Inthat case, the fabric tube must be cut open as described below to removethe fabric product from the spars.

As best shown in FIG. 9, the process begins with the three-portionfabric strip 40 being pulled from supply roll 72 by drive nip roll set74-75. Controlled feed rate of the strip between supply roll 72 and niproll set 60 is provided by motor-controlling signals from dancer 73.Constant tension in the strip between nip roll set 74-75 and drive nipset 60 is provided by motor-controlling signals from tension-sensingroll 76, as explained above. The strip is directed past glue applicators78, and the upper, glue line-bearing side of the strip is inverted byroller 76 so that such glue lines come face-to-face with the precedingwinding between the rolls of nip roll set 60. There, the glue joint isclosed and the overlapping windings are bonded to each other.

As will be appreciated by reference to FIG. 5, the infeeding strip 40,with glue lines 42, 44 already applied by applicators 78, must preciselyregister with the preceding winding traveling on the upper reach of thefabric loop extending from spar 58, through drag nip roll set 66 todrive nip roll set 60, where infeeding strip 40 first comes into contactwith the preceding winding for bonding. FIG. 9 shows how the skewing ofspar 56 causes the lower reach of the endmost fabric strip winding toshift laterally as it travels to spar 58 and back to the point betweenthe rolls of drive nip roll set 60 where the incoming strip, withfreshly applied glue strips 42,44 on its underside, is pressed againstit. The lateral shift, a result of the helix lead angle, is selected tocause a shift of approximately one-third of the width of strip 40, sothat glue lines 42,44 will register with the previous winding as shownin FIG. 5. Thus, the required relative positioning of the relativelyopaque vane portion 34 with the relatively translucent facing portions30′,32′ will be achieved when the vanes of the finished blind are placedin their light-blocking or fully closed angular setting.

Precise control of the amount of overlap between successive windings isprovided by two independent controllers. First, the lateral position ofinfeeding strip 40 from supply roll 72 is provided by a controller (notshown), or other known web guiding device, which laterally shifts theplacement of roll 72 along its rotational axis.

Secondly, additional control of registration of the overlapping windingsof strip 40 is provided by drag nip roll set 66, which has a “steering”capability. Both pressure rolls 64 and 70 are rubber-coated, to providea compressible surface. Unlike pressure roll 64 of drive nip roll set60, which has a constant force pressing it downward toward drive roll62, steering pressure roll 70 has independently controllable downwardpressure (described below) applied at its opposite ends. When theapplied pressures are equal at both ends of roll 70, the roll has astrip-contact zone of uniform width along its entire length, where therubber roll is deformed about the unyielding surface of roll 68. Thepassing fabric strip does not deviate from its straight-line path, andcontinues to take the shortest route from spar 58 to nip roll set 60. Anincrease in the nip pressure at one end of roll 70 increases theconcavity of its rubber-coated surface as it is deformed by thecylindrical contour of the non-yielding surface of lower roll 68. Thepath of the fabric strip at that end of the roll lengthens as it isforced to assume the longer curved shape of the further deformed surfaceof roll 70. That is, the strip-contact zone (at that end) between theopposed rolls of nip roll set 66 increases to a greater segment of anarc about the rigid roll's surface resulting from the extra deformationof the surface of roll 70 straddling a lengthened portion of theperimeter of lower roll 68. The resulting longer strip path on the edgewith increased steering pressure creates increased strip tension on thatedge, pulling or steering the fabric toward that edge. Reducing pressureat one end similarly reduces the path there relative to the nominalcondition, drawing the web toward its other edge.

FIGS. 15-17 schematically illustrate a steering control system forvarying the pneumatic pressure applied to cylinder P1 on one end ofpressure roll 70. That end of pressure roll 70 is mounted in verticallyslideable bearings. The control signal is provided by a proportionalvoltage output device in the form of an edge-position sensor 92, whichmay be in the form of a linear array of light-emitting outputs andphotocells on opposite sides of the plane of the passing fabrics. Anydeviation from the desired edge position of the strip generates acorresponding deviation from a nominal pressure-demand voltage signalsent by sensor 92 to control computer/proportional regulating valve 94.Valve 94 bleeds or supplies air pressure from source 96 as required tomaintain a desired cylinder pressure defined by the voltage signal. Theresulting tilting and deformation of roll 70 is shown in exaggeratedform in FIGS. 15-16, and the corrected path of the upper reach of fabrictube 88 is shown in the plan view of FIG. 17.

While the use of crowned rolls to “steer” a web or flat belt to acentral position, and the use of flared-end rollers to spread andde-wrinkle a web, are well known, it is believed that the use of aselectively deformable roller at a nip to steer a web by local controlof path length is novel. Those skilled in the art will recognize thatsteering can be achieved either by varying the pressure on both ends, ormaintaining nip pressure constant on one end while increasing ordecreasing the pressure on the other end, as required.

Because fabric strip 40 has a helix lead angle as it winds onto spar 56(which is skewed by such angle relative to drive nip roll set 60), thefabric “tube” 88 continuously advances toward the opposite end of thenon-rotating spars. The spars, which do not rotate, are highly polishedto facilitate this sliding movement without damage to the fabric.

The spars are preferably sufficiently long to permit them to hold anentire tube formed from a feed roll. For example, a machine has beenbuilt with twelve-foot long spars, for use with a three hundred-yardlong feed roll. The spars may be perforated to permit pressurized air toprovide an air bearing to reduce the drag of the fabric tube as itadvances along the spars. When the machine is shut down to install afresh feed roll, the tube may be cut off, using a scissors, by firstcutting around the circumference of the tube, generally along a givenstrip. Alternatively, a razor knife may be plunged through thestill-forming tube, just beyond the ends of nip sets 60, 66, and held inposition for one full rotation of the tube. Then the knife is drawnquickly across the severed winding to separate the formed length of tubedownstream from the still-forming tube upstream. The separated tube isthen slid away along the spars and cut open along line C—C while themachine continues to form more tube. Then, the severed tube, while stillhanging on the spars, is cut along a line C—C (see FIGS. 15-16), whichis perpendicular to the edge of the windings, so that the tube may belaid open to form a parallel-edged flat form or slab 90 with the woundstrips perpendicular to the parallel edges. If an automatic splicer isfitted to the supply roller 72, the operation of the machine can be thusmade continuous.

In the presently constructed machine, the cut open product slab 90 isabout ten feet wide and about ten or more feet long. The fabric slab isthen cut to size for particular windows, and the fabric Venetian blindis fully formed except for its connection to a wind-up roll andassociated hardware.

Many different products and visual effects can be achieved by use of thepresent invention. A basic Venetian blind may preferably be formed ofpolyester (for strength and UV resistance) knitted mesh front and rear,of different mesh patterns, and a knitted polyester relatively opaquefabric for the vanes. Where minimization of the moire effect is not aprimary concern, the same fabric may be used for the front and rearfacing panels. A preferred fabric is a stabilized tricot of 28 gage 20/1semi dull polyester, manufactured by Gehring Tricot Corporation, andidentified as P201. Stabilized tricots provide a preferred combinationof visual sheerness with a high degree of structural stability for easein handling during manufacture. Where moiré effect minimization is aconcern, then such fabric may preferably be paired with a rear facingfabric in the form of a diamond tulle, such as 36 gage, 20/12 brightpolyester, manufactured by Gehring, and identified as P1732. Therelatively opaque vane may be a jersey fabric, 70/33, 20/1 semi-dulltextured polyester, like that manufactured by Native Textiles, andidentified as P7020.

A significant advantage of the use of the helical strip-windingtechnique of the present invention is that the resulting front and rearsheer panels, being composites of multiple, narrow, horizontallydisposed sheer strips, tend to suppress objectionable moire effectswhich would arise if the same choice of fabrics were used in the form ofsingle-sheet, continuous panels for the entire front and rear facings.Tricot type fabric, a preferred form of weave, has heavily barredpatterns extending in the longitudinal or “machine direction” of thefabric as it is manufactured. When such barring is oriented in thevertical direction (of a normally hanging window shade) for continuousmanufacture of single panel facing, a cross-grid pattern is establishedwith the horizontally oriented vanes and vane shadows, leading to arelatively dramatic and objectionable moiré effect. With thestrip-winding technique disclosed herein, the sheer strips andassociated machine-direction bars of the tricot fabric can be orientedhorizontally. In this orientation, the barring pattern does not form across grid with the vanes, but tends to blend in with the parallel vanesand vane shadows. Also, the multiplicity of narrow sheer strips acts tobreak up otherwise large-scale moire patterns into smaller, morelocalized, banding patterns which are less objectionable. Still further,the individual sheer strips tend to be slightly tilted or bowed relativeto each other, rather than more truly parallel, as in the case facingpanels formed of single, continuous sheets. This fact, along with small,local differences in tension and alignment of individual threads inadjacent wraps, further diminishes large scale coherence in the moireinterference patterns.

Alternatively, other knits, wovens or nonwovens may be used for eitherthe facings or vanes, and hot-melts, pressure sensitives, tapes or otheradhesives may also be used, provided they possess UV resistance,non-yellowing and strength with no flow at up to 200 degrees Fahrenheitfor durability in sunlit windows.

While many of the known glues can be used, hot-melt adhesives arepreferred, such as the high-temperature polyester manufactured by Bostikand identified as 7199 or W4360B. This type of adhesive is advantageousbecause of the ability to be precisely metered through applicationnozzles, high initial tack, rapid cure to a flexible final state,ultraviolet resistance for use in sunlit windows and minimum ofbleed-through adhesion as a result of the rapid cooling of its surfaceonce applied. Alternatively, moisture-cure polyurethane hot-appliedglue, such as HL-9608 manufactured by H. B. Fuller, has many of the samefeatures, plus added strength and flexibility once cured, but thesebenefits must be considered in light of slower curing and associatedbleed-through tendencies.

Another alternative Venetian blind product which may be formed by thishelical winding technique would use fabric of uniform light-transmittingability throughout. That is, instead of a three-segmnent strip ofvarying opacity, the winding strip could be made of a single,ultralight, non-woven fabric. In the “open” position, light would befiltered through two layers (the front and rear composite facings),while in the partially and fully closed positions, it would be furtherfiltered through the vane layer of fabric, causing an additional fiftypercent diminution in the light transmission through the blind. Ifangle-dependent polarizing material were used, further control of thelight transmission could be obtained.

Because this helical winding process permits use of narrow strips ofmaterial to form the composite facing panels, the face panels can beformed of lace material. Heretofore, continuous sheet facing panels weretoo wide to permit lace to be used at an acceptable price. Also, itwould be difficult to match the pitch of the finished shade to therepeats of the wide-goods lace. As further alternatives, the vaneportion may be a thin wood veneer laminate, or printed cloth withdifferent colors on its opposite sides.

The modified embodiment of FIG. 18 is similar to the embodiment of FIG.5, but employs a different means of opacifying the center or vaneportion of each strip. These pocketed strips 102 each compriseoverlapping rear and front sheer facings 104, 106, respectively,pre-joined (i.e., prior to winding) by glue lines or ultrasonicjunctions 108. The central overlapping thirds and glue lines define aninsert-receiving pocket 110. Strips 102 are wound and bonded together atglue lines 112, as in the previously described embodiment of FIGS. 5, 9and 10. Later, after cutting open the helically wound tube, opaqueinserts 114 may be inserted in pockets 110 to provide the desired opaquevanes. As a further alternative, the pocketed strips can have the senseof the overlap reversed. That is, front sheer facing 106 can overlaprear sheer facing 104. Alternatively, the individual facing strips 104,106 and a continuous strip of opaque insert 114 can be helically woundtogether by use of multiple feed rolls 72 appropriately positioned tofeed with the desired overlaps onto the winder.

FIG. 19 illustrates an example of a double-deep structure havingmultiple rows of vanes or central ligaments. Each strip 116 comprisesfive segments, namely, rear, front and central sheer portions 118, 120,122, respectively, and first and second opacified portions 124, 126,respectively. Successive strips are helically wound and bonded togetherat glue lines 128, as previously described. Opacified portions 124, 126could have different degrees of opacity, so that, depending upon whichcolumn of vanes was closed, a light-blocking or a semi-translucent modecould be selected. Alternatively, these two portions could becross-polarized to provide a choice of opacities. With both vanes fullyopen, a transparent light path would be provided through the alignedsheer portions 118, 120, 122.

By shortening the length of central ligament or sheer portion 122, itwill “go straight” or taut before the front and rear facings, providinguniform pitch for the hanging blind, and allowing the front and rearfacing segments 118 and 120 to assume a softer, slightly looped orcurving, appearance.

In an alternative winding process, a multi-lead winding arrangement canbe employed. A first such arrangement, illustrated in FIG. 20,introduces a second distinct pre-formed three-portion strip 40 b from aseparate supply roll 72. For the simplicity of illustration, dancer 73has been omitted from this Figure, as well as from the furtheralternative illustrated in FIG. 21. A similar pair of glue nozzles 78 bis provided to apply glue stripes to strip 40 b in the same manner andlocation as in the case of the primary strip 40 a. Because the fabricloop or tube 88 is lengthened by two non-overlapping strip portions perrevolution, rather than one, the helix lead angle must be doubled. Thatis, the angle between spars 56, 58 and nip sets 60 and 66 must bedoubled.

A second multi-feed arrangement is illustrated in FIG. 21. Instead offeeding a pre-formed three-portion strip from supply roll 72, theindividual portions of the strip can be fed from separate supply rollsand joined to each other (with minimal overlap) as they are laid uponand joined to the previously applied winding of fabric tube 88. Thesejunctions are preferably achieved by ultrasonic welding, but glue linesmay alternatively be used. In FIG. 21, three supply rolls simultaneouslyfeed separate strip portions 40 a, 40 b and 40 c. Only a single glueline (from nozzle 78 a) is required to secure portion 40 a to the priorwinding or wrap. Similarly, only a single glue line (from nozzle 78 c)is required to secure central portion 40 c to adjacent portion 40 b ofthe same wrap. However, two widely spaced glue lines (from nozzles 78 b)are required to join central portion 40 b to portion 40 a of the samewrap and to separately join portion 40 b to portion 40 c of the priorwrap. Note that two or more strip portions (here, portions 40 a and 40b) can be fed into the fabric loop at the same place, i.e., at nip set66, with an offset equal to the desired offset per lap or wrap. A stripportion (here, portion 40 c) can also be fed in at a separate locationon the fabric loop, i.e., at nip set 60. As long as the feed-inlocations are within the flat portion of the fabric loop 88, the offsetremains equal to the desired offset per lap in the finished goods.

FIG. 23 shows, with the vertical scale exaggerated for clarity, a priorart three-element strip construction used to form the fabric Venetianblind disclosed in U.S. Pat. No. 5,888,639. Strip 130 comprises anopacified vane portion 132 whose opposite longitudinal edges areultrasonically welded to front and rear sheer strips 134, 136,respectively (each shown as a small “x”), at weld lines 138, 140respectively. The relatively opaque strip is wider than the sheerstrips, and the sheers are aligned with the opposite edges of the opaquestrip. Thus, there is only one sheer present at each edge, allowing athrough-welding of one sheer to each edge of the relatively opaquestrip. This prior art process then subjects the welded three-elementstrip to a series of operations, including edge trimming, opening of thewelded joints (as shown by dotted lines in FIG. 23), and flattening toultimately obtain a flattened, three-element strip. The resulting stripis then cut to a length corresponding with the width of the window intowhich the blind is to be inserted. The cut-to-length strips are then,according to this prior art disclosure, stacked and bonded together,using a technique substantially different from the helical windingtechnique disclosed herein.

FIG. 24 is a view similar to FIG. 23, but showing a modifiedthree-element strip construction according to one embodiment of thepresent invention. Unlike the three-element strip constructions of eachof FIGS. 6, 7 and 8 of the present invention, and also unlike the priorart configuration of FIG. 23, the construction of three-element strip142 of FIG. 24 comprises a relatively opaque strip 144 to which onesheer strip 146 (which may be the front sheer strip) is lapped slightlythereunder and preferably ultrasonically welded at weld line 148, justas in the embodiment of FIG. 6, while the other sheer strip 150 (whichmay be the rear sheer strip) is aligned with the opposite edge ofrelatively opaque strip 144, and in fully overlapping relationshipthereto, and welded at weld line 152.

The resulting “half-lapped” three-element strip 142 is then helicallywound, as shown in FIG. 25, with the double-thick edge of incoming strip142 a closer to the previously formed winding 142 b of the helix. FIG.25 is a view generally in the direction of left to right in FIG. 9, butshowing a modified assembly sequence adapted for winding the half-lappedstrip 142. For clarity of illustration only, drive nip roll set 60,tension sensing roll 76 and idler roll 162 have been omitted from FIG.25. This fragmentary perspective view shows the incoming strip 142 a asit turns over the omitted tension sensing roll 76 and idler roll 162just prior to interfitting with the immediately preceding wrap 142 b. Asis evident in FIG. 25, the trailing edge of the helix, namely, the freeedge of rear sheer strip 150 b, is temporarily lifted up or partiallycurled back from underlying opaque strip 144 b by picker or finger 164just upstream from the zone where the incoming three-element strip 142 ais brought into alignment to join the previously wound helix. Thislifting action permits the double-thick edge of incoming strip 142 a toenter that gap beneath rear sheer strip 150 b and slightly overlaprelatively opaque strip 144 b.

The lifting action is accomplished by a finger 164 illustrated in FIGS.30-31. Only a slight modification to the winding apparatus of FIGS. 9-10is required to adapt it to the use of half-lapped three-element strip142. The fragmentary perspective view of FIG. 30 is taken generally inthe direction of left to right in the unmodified apparatus of FIG. 9,but with drive nip roll set 60, tension sensing roll 76 and idler roll162 (which is added for use with strip 142) omitted for visual clarityonly. FIG. 31 is a fragmentary plan view of the zone of FIG. 30 wherethe incoming strip 142 a is engaged by finger 164 and interfits with thepreceding winding 142 b.

As compared with the apparatus illustrated in FIGS. 9-10, two structuralchanges appear in FIGS. 30-31. First, idler roll 162 has been added, tore-direct the infeeding strip so that it has a horizontal runimmediately upstream of nip rolls 62,64. This horizontal run isnecessary so that the incoming and preceding windings can be properlyinterfit with each other for bonding. Second, finger 164 has been addedas an aid in opening up the trailing free edge of rear sheer strip 150 bof the preceding winding so that it can receive the double-thick edge ofincoming strip 142 a.

Referring to FIGS. 25, 30 and 31, it will be seen that the trailing freeedge of rear sheer strip 150 b is pushed laterally and lifted slightlyby finger 164, which is mounted on the end of support rod 170. Toaccomplish that shifting, finger 164 has a lower horizontal ledgeportion 166, shown in dotted lines in the plan view of FIG. 31, whichthe free edge of sheer strip 150 b rides upon as it moves toward idlerroll 162. As a portion of such strip edge is lifted onto ledge 166, itis then engaged by a generally vertical leg 168 of finger 164. Verticalleg 168 cooperates with horizontal ledge portion 166 to laterally shiftas well as lift the edge of strip 150 b for a sufficient longitudinalrunning length to permit the double-thick edge of incoming three-elementstrip 142 a, which is offset from the previously wound wrap 142 b by thehelix lead, to overlap the relatively opaque and lower or front sheerportions 144 b and 146b, respectively, of previously wound wrap 142 b,and tuck in underneath the lifted edge of upper or rear sheer 150 b.

Application of front glue line 154 is accomplished by an applicator (notshown) located immediately above the double-thick, interfitting edge ofrear sheer strip 150 a and downstream from idler roll 162, that is, at apoint where the free edge of the rear sheer strip 150 b of the precedingwrap is still curled back to expose the glue-receiving edge of strip 150a (see FIGS. 25 and 31). After that overlapping relationship isestablished between the double-thick edge of incoming strip 142 a andthe underlying relatively opaque vane 144 b of previously wound strip142 b (see FIGS. 25 and 31), the overlapping portion of strip 142 amoves beyond vertical leg 168 of finger 164 (i.e., below the finger asviewed in FIG. 31) and returned to a flat-lying condition. The undersideof the now lowered free edge of rear sheer strip 150 b will then contactglue strip 156 on the upwardly facing edge of incoming rear sheer strip150 a to permit the required bond to be created.

The horizontal ledge portion 166 of finger 164 may serve an additionalpurpose. Where the glue line is shifted away from the underlying weldedjoint, as shown in the embodiment of FIG. 27, there is a tendency forthe glue to bleed through the underlying sheer and temporarily form afragile, weak attachment to the underlying relatively opaque vane. Thisunintended attachment would typically break the first time that thecells are fully opened, allowing the assembled panel to functionnormally, with the vanes fully free except at their welded joints.However, assuring such spontaneous separations occur uniformly andtotally throughout the entire product may require a closer and morecostly control of glue application than otherwise necessary. Thisproblem can be completely avoided by dimensioning ledge portion 166 sothat its left edge (as viewed in FIG. 31) is positioned to separate anytemporary glue attachment resulting from bleed through of glue betweensheers 150 b and 150 c.

Referring again to FIG. 25, front glue line 154 has already been appliedto front sheer 146 a of incoming strip 142 a before it makes the turnaround roll 76, as shown in the upper right of portion FIG. 25. Thus,glue line 154 will be properly positioned on the lower side of the stripfor engagement with and bonding to preceding front sheer 146 b. Rearglue line 156, however, must be on the upwardly facing side of rearsheer strip 150 a in order to engage and bond to the underside of theuplifted trailing edge of rear sheer strip 150 b. Therefore, theapplicator (not shown) for glue line 156 must be located to apply theglue after the strip has passed roll 76 and before it passes under drivepressure roll 64.

The resulting helix is cut open, as previously described, and cut tosize for particular windows. FIG. 26 shows the end view of the resultingcellular structure in its partially open condition. It is evident that,in contrast to the structures of FIGS. 3-8, the two sheer strips of agiven three-element strip form the front and rear portion of the same,rather than adjacent, cells. Significantly, another difference is thatthe direction of lapping of adjacent facing segments is the same on boththe front and rear of the resulting panel. That is, e.g., rear sheersegment 150 b overlaps adjacent rear sheer segment 150 a, just as frontshear segment 146 b overlaps adjacent front sheer segment 146 a. Thisconfiguration is advantageous in that, if the fabric Venetian blind ismounted so that the overlap is oriented shingle style, both front andrear facing panels will be so oriented, and the exposed sheer edges willless likely to collect dust or fray from contact with downwardlydirected cleaning strokes or falling objects.

Furthermore, overlaying one of the sheer strips onto the stifferrelatively opaque vane reduces the instability of the three-elementstrip, thereby improving wrap-to-wrap alignment and the smoothness ofthe assembled composite facing panels. This advantage is particularlybeneficial when using extremely fine knits such as diamond tulle, whichis preferred in conjunction with a tricot knit for the opposite facewhen reduction of the moire effect is desired.

FIG. 27 shows a modified version of FIG. 26. As in the differencebetween the embodiments of FIG. 22 and FIG. 5, the modification resultsfrom a shifting of the location of glue lines 154′ and 156′. Therelocation of the glue lines away from the weld lines 148, 152,respectively, creates inwardly projecting front and rear sheer tabs 158′and 160′, respectively.

FIG. 28 shows the same three-element strip structure and orientation asshown in FIG. 25, except that glue lines 154 and 156 have been initiallyapplied to the opposite elements of the to-be-bonded surfaces. That is,front glue line has been shifted from the lower side of the left edge ofincoming front sheer strip 146 a (as shown in FIG. 25) to the upper sideof the right edge of the front sheer strip 146 b″ of the preceding wrapof the helix (as shown in FIG. 28). Similarly, rear glue line 156 in theFIG. 28 illustration is applied to the curled back, upwardly facing,underside of the rear sheer strip trailing edge of the previously woundthree-element strip 142 b″. An appropriate picker or finger (not shown)would be provided to temporarily curl back and invert that trailing edgeof rear sheer strip 150 b″.

FIG. 29 shows a further modification of the manner of winding thethree-element strip of FIG. 24. In this embodiment, the orientation ofthe strip is reversed, with the double-thick edge of the previouslywound strip trailing rather than leading. Therefore, the free edge ofthe incoming rear sheer strip 150 a′″ must be opened and curled back toreceive rear glue line 156′″ and to permit entry of the double-thicktrailing edge of preceding wound strip 142 b′″, and then uncurled toenclose such trailing edge. This arrangement presents greater alignmentand guidance difficulties, and is therefore not preferred.

FIGS. 32a-32 b through FIGS. 38a-38 b show additional embodiments ofthree-element strips. As in the case of FIGS. 23 and 24, the proportionsof the strips in these drawings are exaggerated for clarity, and thelocation of the weld lines is shown with an “x”. The relatively opaquevanes are shown with cross-hatching. Within each numbered pair ofdrawings, the “a” Figure shows the three strip portions in theirflattened condition as welded, while the “b” Figure shows thethree-element strip partially opened as it would be in thelight-admitting position within a fabric Venetian blind.

In the light of the foregoing explanation of the winding and assemblytechnique employed with the embodiment of FIG. 24, those skilled in theart will understand how to wind and assemble these alternativethree-element strip configurations. The embodiments of FIGS. 36-42 wouldrequire, during the winding operation, a temporary lifting of thepreviously wound upper sheer free end to allow tucking under the edge ofthe incoming three-element strip, as described above with reference toFIGS. 25 and 30-31. It will also be recognized that a choice exists asto which element will overlap the other at the required glue jointsbetween adjacent three-element strips. That is, by way of example, eachof the glue joints required for adjacent three-element strips accordingto the embodiments of FIGS. 32-35 can only be made with the incomingwinding as the overlapping element at each joint. Conversely, in theembodiments which are generally Z-shaped, such as FIG. 38, both freeedges of the incoming three-element strip can be either overlaid ortucked under the corresponding portion of the previously woundthree-element strip. In the configurations of FIGS. 36 and 37, the uppersheer (as shown in the Figures) can only overlap, whereas the lowersheer can overlap or tuck under, as desired.

The embodiments of FIGS. 39-42 show two-element strips which are formedwith a pocket for subsequent insertion of a preferably semi-rigid opaquevane, which vanes are shown in the “b” Figures of each numbered pair.Otherwise, the same winding and assembly considerations as discussedabove apply.

As discussed with respect to the embodiment of FIG. 27, each of theseembodiments of FIGS. 32-42 can be constructed as shown, with the glueline between adjacent windings essentially overlying previously formedweld joints in the overlapped winding, or they may have the glue lineshifted laterally away from such weld line (as shown in FIG. 27),creating a short, inwardly projecting sheer tab or ligament.

While the helical winding technique disclosed herein is normally thepreferred technique for assembling the three-element strips into anarray of cells, some circumstances may make it preferable to initiallycut the three-element strips to length and then overlap them instaggered, parallel alignment for joining them together. One suchcircumstance is where the material chosen for the relatively opaquevanes is not suitable for the repeated longitudinal bending experiencedas the strip traverses the various rolls in the disclosed helicalwinding operation. In that event, a cutting and assembling techniquesuch as disclosed in the previously mentioned U.S. Pat. No. 5,888,639may be preferred.

Another advantage of the constructions disclosed herein is that they alllend themselves to simple lap joints, parallel to the plane of thefacing panels, at the points of attachment of successive strips to eachother. When so joined, the smooth, generally planar character of thefacing panels is more likely to be maintained at the joints. Lap jointsso constructed and positioned are to be contrasted with the inwardlyturned tabs, perpendicular to the facing panels, such as disclosed inFIGS. 11 and 11a of U.S. Pat. No. 5,888,639, which is more typical ofhoneycomb type cellular constructions as shown in FIG. 1 of that patent.The latter construction requires an additional folding step forassembly, and, unless there are post-assembly creases set at the facejoints, it will not lie flat. Furthermore, if it is creased to make thefaces lie flat, the vanes will not lie closed naturally or fully (asdesired) and will not make the desired curving shapes when open.

Another advantage of the half-lap three-element strip, as exemplified byFIG. 24 and 26 hereof, is that when the strip is spooled into roll 40after welding, the double-thick portion is wide and stable enough tomake a smooth, uniform roll with no distortion of the material.Subsequently, during the winding and gluing steps, this type of striphas improved directional stability and flatness, resulting in a smootherand more uniform product.

FIG. 43 illustrates a still further three-element strip configuration172 wherein both front and rear sheer strips are bonded to the same faceof the opacified strip. The term bonded includes any suitable techniquefor joining the strip elements together including, but not limited to,gluing, welding and/or sewing. Front sheer strip 176 is bonded at 178 toopacified strip 174, while rear sheer strip 180 is bonded at 182 to theopposite end of opacified strip 174.

In positioning and gluing successive three-element strips in partiallyoverlapping position, according to the method described with respect toother embodiments hereof (see FIG. 44), front glue line 184 ispreferably placed directly over front bond line 178, to minimize anypossible glue bleed-through problems. Rear glue line 186 is preferablyoffset from rear bond line 182, thereby creating a short internal sheertab between rear bond line 182 and rear glue line 186. By way ofexample, front sheer strip 176 may be approximately one andthree-quarters inches in width, rear sheer strip 180 approximately oneand seven-eighths inches in width, and opacified strip 174 approximatelytwo and one-eighth inches in width. With those dimensions, the width ofthe internal sheer tab between rear bond line 182 and rear glue line 186may be about one thirty-second to one sixteenth of an inch. Theresulting sheer tabs are contiguous parts of the sheer composite sheet(180 a+180 b+180 c, etc . . . ) that results from the bonding togetherat rear glue line 186 of adjacent rear sheer strips 180. Any minor gluebleed-through at this rear location creates no problems because thesheer fabric layer in this region are backed only by a steel roll duringthe fabrication process.

Still further alternatives (not illustrated) for use of a three-elementstrip similar to the FIG. 43 embodiment could utilize glue lineplacement to create sheer tabs on the front side of the blind and/or toeliminate the sheer tabs on the rear side.

This invention may be further developed within the scope of thefollowing claims. Accordingly, the above specification is to beinterpreted as illustrative of only a few operative embodiments of theinvention, and not in a strictly limiting sense. In the followingclaims, the words “right”, “left”, “upper” and “lower” have been used asrelative orthogonal directions for ease of description only, and are notintended to be defined in relation to any external datum, such as thesurface of the Earth. Also, “edge” or “edges”, as used in the claims,means the extreme lateral edges of the strips or strip portion faces,along with a relatively narrow immediately adjacent portion of suchfaces.

We claim:
 1. A light-control panel comprising: a first three-elementstrip including a first elongated light-transmitting strip portionhaving a left edge bonded to a left longitudinally extending edge of anelongated, relatively opaque strip portion at a first bond line and asecond elongated light-transmitting strip portion having a left edgebonded to a right longitudinally extending edge of said opaque stripportion at a second bond line; a second three-element strip having afirst elongated light-transmitting strip portion having a left edgebonded to a left longitudinally extending edge of an elongated,relatively opaque strip portion at a first bond line and a secondelongated light-transmitting strip portion having a left edge bonded toa right longitudinally extending edge of said opaque strip portion at asecond bond line; a right edge of said first elongated strip portion ofsaid first three-element strip being bonded to a left edge of said firstelongated strip portion of said second three-element strip at a thirdbond line that is substantially directly over the first bond line of thesecond three-element strip; and a right edge of said second elongatedstrip portion of said first three-element strip being bonded adjacent toa left edge of said second elongated strip portion of said secondthree-element strip at a fourth bond line that is offset from the secondbond line of the second three-element strip to form an elongated cell.